Control of AC motor/generators, such as three-phase permanent magnet synchronous electric motors (electric machines) is accomplished using a three-phase pulsewidth-modulated (PWM) inverter. A PWM inverter can be controlled in several different operation modes, including, e.g., a space vector PWM (SVPWM) mode and a six-step mode. Magnitude of the output voltage from an inverter at its fundamental frequency reaches its maximum only when the inverter operates in the six-step mode. Due to this voltage magnitude characteristic, operation in the six-step mode can increase torque capability of an electric machine compared to known SVPWM operation or discontinuous space vector PWM (DPWM) operation in the field-weakening region where the voltage magnitude is the major limiting factor of the torque capability. However, voltage magnitude is not controllable in the six-step mode. Furthermore, known methods for frequency-synchronized control of an inverter operating in the six-step mode require updating and potentially changing sampling frequency of the controller each sampling period to minimize sub-harmonics, which can be computationally taxing on the controller.